FIG. 1 shows a conventional door mirror assembly in which a visor thereof is electrically driven. In the figure, a reference numeral 1 points to a stay which is fixed to a door of an automobile, and a reference numeral 2 points to a visor which is rotatably mounted on the stay 1. As shown in FIG. 2, the visor 2 of the door mirror assembly is rotatable with respect to the stay 1 between a using position, a housing position which is located behind the using position and an emergency escaping position which is located in front of the using position. The visor 2 is electrically driven by an electric driving system, a part of which is mounted on the stay 1, and a part of which is mounted on the visor 2.
The visor 2 has an inner bottom surface C2-1 and an inner side surface C1-1. On the other hand, the stay 1 has a generally horizontal surface C2-2 which supports the inner bottom surface C2-1 of the visor 2 from below, and has a longitudinal surface C1-2 which faces the visor 2 in parallel with the inner side surface C1-1 of the visor 2, where there are formed a gap C1 and a gap C2, therebetween, respectively. These gaps C1 and C2 are necessary elements required to let the visor 2 rotate smoothly with respect to the stay 1. Therefore, it is not possible to make the gaps C1 and C2 very small.
However, if the gaps C1 and C2 are more than 0.4 mm therebetween, there arises a problem that the gaps may cause a whistle effect to generate an air-striking sound when the automobile runs at a high speed. The more silent and quieter the interior of the automobile is, the more notieceable and pronounced the air-striking sound becomes due to the whistle effect. In order to solve this problem, such a countermeasure has been conventionally taken, for example, as to put a sponge body between the gaps or as to implant artificial hair on a surface forming the gaps, so as not to hinder the rotation of the visor. However, with the use of such means for a countermeasure, it is necessary to provide the gaps with the additional member(s) thereof; therefore, there arises a problem that the additional member(s) deteriorate(s) and/or become(s) worn with age.
Observing the necessity of the gaps therebetween, it is found that they are necessary only during times when the visor is rotated, that they are not necessary the visor is in the using position.